Behar. Res. Ther. Vol 23. No. 5. pp. 563-569. 1985 0005-7967185 $3.00 + 0.00 Printed in Great Britain. All rights reserved Copyright i% 1985 Pergamon Press Ltd

SELECTIVE PROCESSING OF THREAT CUES IN ANXIETY STATES

ANDREW MATHEWS and COLIN MACLEOD Department of Psychology. St George’s Hospital Medical School, Tooting, London SWl7, England

(Received I? December 1984)

Summary-It was postulated that generalized anxiety states are associated with selective processing of threat cues arising from the activity of cognitive structures concerned with processing information related to personal danger (danger schemata). Selective processing was investigated using a modification of the Stroop Colour-naming Task, in which some of the target words were related to physical or social threat, while others were completely unrelated to danger. Anxious Ss were generally slower than controls in colour-naming all words, but were particularly slow with threat words. In the case of physical (but not social) threat words, there was also evidence that interference was most marked in those Ss reporting worries within the relevant domain. Taken together with correlational findings that degree of slowing was associated with mood state, the results were interpreted as evidence that the individual content of danger schemata determine the type of material that is selectively processed, while the extent of interference observed depends on current anxiety level.

INTRODUCTION

Generalized anxiety states are commonly regarded as non-situational; that is, anxiety is thought to arise from some internal process or dysfunction rather than provoked by external situations as with phobic anxiety. Clinical observations have led some authors to suggest that anxiety of this type is initiated or maintained by internal cues such as thoughts or images related to personal danger (Beck, Laude and Bohnert, 1974; Hibbert, 1984). Bodily sensations have also been claimed to give rise to anxiety when they are interpreted in an alarming way. Symptoms such as dizziness for example. that arise from overbreathing may be misinterpreted as indicating physical disease or collapse. The resultant alarm can lead to further hyperventilation which maintains or increases anxiety still further, thus precipitating a full panic attack.

Subjective reports of danger-related ideas at times of increased anxiety are of course subject to several potential sources of bias. These biases include both interviewer demand and culturally determined or common-sense theories held by the anxious individual. Furthermore, in the absence of appropriate control groups, it remains unclear whether or not similar reports might be obtained from all Ss, whether or not they complain of clinical anxiety.

In an earlier study, Butler and Mathews (1983) attempted to overcome some of these problems by asking Ss to estimate the subjective probability of a range of hypothetical dangers. In the case of anxious Ss, estimated probability of dangers was most strikingly inflated in the case of events related to oneself, as opposed to other people. Such effects may be seen ai the temporary consequence of negative mood states, whether anxiety or depression. However, further work with normal Ss (Butler and Mathews, 1985) showed that a generalized inflation of subjective risk across a range of events is particularly characteristic of those with high trait anxiety. It would therefore seem that both high-trait-anxious normals, and individuals experiencing clinical anxiety states, are characterized by a generalized tendency to overestimate personal danger.

There are many possible explanations that could be put forward to account for these findings, but one theoretical framework that we have found useful implicates the activity of cognitive structures involved in evaluating personal threat (danger schemata). Specifically, we propose that anxiety is associated with a bias in processing information related to threat, due either to differences in type or extent of such schemata, or to the ease with which they can be activated.

The origins of such schemata, and the necessary conditions for their activation, are not further specified here, although they may plausibly be argued to arise from the past experience of actual danger events (cf. Finlay-Jones and Brown, 1981). Even if such events are involved in the development of danger schemata, the fact that some individuals experience similar events without

564 ANDREW MAI-HEWS and COLIN MACLEOD

developing anxiety states, suggests to us that other personaiity or cognitive differences are also relevant. Rather than expioring this issue further. it is intended here to examine the question of whether individuals experiencing anxiety states are indeed characterized by selective processing of danger-related cues.

In the present study the extent to which anxious individuals allocate processing resources to cues related to possible danger was examined using a modification of the Stroop Colour-naming Task (Stroop. 1938). In the usual form of this task Ss are required to name the ink colour in which words are written and to ignore the word content. Colour-naming is known to be significantly slowed if the words themselves are colour names that conflict with the colour of the ink in which they are written. Subsequent studies have extended this original finding by demonstrating that interference phenomena occur whenever cognitive representations corresponding to the meaning of the words to be colour-named are simultaneously activated. For example, priming the word meaning by requiring Ss to learn another word semantically related to the target. also interferes with colour-naming (Warren, 1972).

Emotional state may also contribute to the apparent extent of interference. as shown by the increase in errors when items are presented at a fixed rate to Ss threatened with electric shock (Pallak, Pittman, Heller and Munson, 1975). Unpublished experiments carried out by Clore in Bower’s laboratory similarly indicated that induction of emotional states may be associated with slowed colour-naming for all emotional words, whether positive or negative (cited by Bower. 198 I. p. 142). A study by Geller and Shaver (1976) further demonstrated that interference with colour-naming self-referent (but not other) words occurred only in Ss who had been made self-aware by performing in the presence of a mirror and camera. Most directly relevant to the present study is recent work by Watts, McKenna, Sharrock and Trezise (1984) suggesting that spider phobics are selectively slowed in colour-naming words that are related to spiders (e.g. web).

Although there is some doubt as to whether all these interference effects can be attributed to a single mechanism (cf. Stirhng, 1979) it is generally agreed that interference effects occur whenever cognitive representations of the irrelevant word content are simultaneously activated. and thus compete for processing resources, whether this interference occurs at the encoding or response output stage.

The cognitive model outlined earlier thus led us to predict that anxiety should selectively impair colour-naming in the case of words relating to threat, as a consequence of the postulated activity of danger schemata. The colour-naming performance of anxious and non-anxious Ss were therefore compared using both danger-related and frequency-matched non-danger-related words. Because previous clinical studies of anxiety states have suggested both physical and social threats as common cognitive themes, words relevant to both these threat domains were equivalently represented. As an initial test of whether any effect could be attributed to better encoding of danger-related words, recognition in memory for the relevant words was also examined.

METHOD

Twenty-four generally anxious out-patients, and an equal number of non-anxious control Ss were required to colour-name words related to physical or social threat. together with others having no threat content. Words with similar content were presented in blocks, and the order of presentation of these blocks was fully balanced within each S group. It was predicted that anxious individuals would take longer to colour-name threatening than non-threatening words, compared with normal controls. Immediately after the colour-naming task. all Ss were given a recognition test consisting of a list of the relevant target words randomly mixed with an equal number of distracters, so as to allow a signal-detection analysis of recognition memory.

Subjects

A total of 48 Ss were tested, 24 of whom had been referred by their General Practitioner for anxiety-management training, and 24 who were selected as controls. Control Ss were matched for age and sex, were mostly employees of St George’s Hospital or Medical School, -and were not

known to be currently receiving help for emotional difficulties. However, control Ss were not

Threat cues in anxiety states 565

Table I. Mean scores for each group on questionnaire measures (all dilTerences significant at less than I”,, level)

Anxious C0ntr0l Measure ss ss

Trait Anxiety 51.8 37.8 State Anxiety 48.0 34.6 BDI 15.3 4.0 MHVT Synonym 19.2 23.7

excluded if they were found to have high Anxiety scores on questionnaire measures, so that some degree of overlap between the groups may exist.

Twelve Ss in both the clinical and normal control groups were male, and 12 were female; mean age for the anxious group was 33.3 yr and the normal control group 31.7 yr. Mean scores for each group on the Trait and State versions of the Spielberger Anxiety Inventory (STAI) are shown in Table 1, together with mean scores from the Beck Depression Inventory (BDI) and the Mill Hill Synonym Vocabulary Test (MHVT). Although groups differed on each of the questionnaire measures, including BDI scores, all referred clients had received a primary diagnosis of anxiety state. Anxious Ss who also complained of substantial phobic avoidance, or whose anxiety was clearly contingent on specific situations, were excluded. Similarly, the presence of obsessional rituals or symptoms indicating a diagnosis other than generalized anxiety, were grounds for exclusion.

Materials

Threat-related words appearing in the descriptions given by Beck et al. (1974) and Hibbert (1984) were selected. in order to maximize their relevance to the reported cognitive content in generalized anxiety disorders. Twelve words were chosen on the basis of their apparent association with physical threat, and 12 were considered to be associated with social threat (see Table 2). Two further sets of positive (non-threat) words were chosen on the basis of frequency-matching with each of the sets of threat words. Each set of 12 words were written a total of 8 times on a large card (A4). the set of 12 being presented in a new random order each of the 8 times. The words were written in block capitals approx. 0.5 cm high, and were coloured either red, green, blue or yellow. The colour assigned to each word was constant across the eight presentations because it was originally intended to test for incidental learning of colours associated with each word (see Table 2). Four cards, each containing 96 words, were constructed in this way, consisting of physical threat. social threat and 2 matched control cards.

For the recognition task, the 48 different words used (24 threat and 24 control) were typed on a sheet of paper, randomly interspersed with 48 distracter words, chosen to be matched in frequency and threat content. Thus there were 12 distracter words relating to physical threat, 12 relating to social threat and another 24 non-threat words.

Procedure

Subjects were not given a detailed rationale, but were asked to help with research into anxiety by completing some questionnaires and simple tests involving words. All Ss then filled out the Spielberger STAI. the BDI and the Synonym section of the MHVT.

Table 2 Words used in each material set. showing colour in which they were written [(B)lue, (Y )ellow. (G)reen OT (R)ed]

PhysIcal threat

Disease(B) Inwr? (Y) Coronary (R) Muulared (B) Fatal(G) Ambulance(R) Coffin (Y 1 Hazard(B) Cancer(G) Deathbed (Y) Emergency (R, Paralysed (G)

Control

Playful (R) Hobby(G) Reassured (B) Secure(Y) Gemal (B) Contented(Y) Carefree (R) Leisure(G) Merriment(R) Satisfaction (Y 1 Cocky(G) Overjoyed (B)

Social threat

Indecisive (Y) Pathetic(R) Foolish (G) Lonely (8) Inferior (Y) Criticized (G) Inept(R) Hated (B) Inadequate(R) Stupid(Y) Failure(G) Embarrassed (B)

Control

Welcome (G) Confident(R) Optimistic (B) Bold (Y) Capable(B) Aloof(Y) Relaxed (R) Windfall (G) Entertamment (R) Assured(Y) Holiday(G) Melody (B)

566 ANDREW MATHEWS and COLIN MACLEOD

Table 3. Mean time (m set) taken hy each group to colour-name 96 threat or non-

threat words

Material

Threat words

Anxious Control SS ss

84.9 65,O Non-threat 80.67 65 8

Each S was then presented with the four cards described above in the order assigned to them within the balanced design, and asked to name the word colours as fast as possible without making errors, and without attending to the word content. Immediately afterwards, recognition memory was tested using the list of target and distraction words. Ss were asked to indicate any of the words that they thought had appeared on the cards. Anxious patients only were asked at the end of the experiment whether they felt that they characteristically worried about physical dangers (such as illness or being attacked) or social dangers (such as failure or what others thought of them). If both domains of concern were reported, patients were encouraged to indicate which one bothered them most, but a chaice was not forced if they indicated that both worried them equally.

RESULTS

As expected, the two groups of Ss differed significantly on each of the STAI scores (P < 0.001, see Table 1). Since BDI scores also differed between the groups, to some extent our generalized anxiety Ss must also be considered to be mildly depressed. Although an attempt had been made to match the graups in occupational status, the anxiety group had significantly lower MHVT scores than control Ss. There were no significant differences in age however.

Mean times to colour-name each card of 96 words are shown in Table 3. These data were analysed using a repeated-measure analysis of variance to detect any effects due to group, valence (threat vs non-threat) and material set (physical vs social). Significant main effects were found for

all three factors, but more importantly there were also significant interactions involving groups x valence [F(l, 46) = 13.6, P c O.OOl] and groups x materials [F( 1,46) = 8.2, P < 0.011. The interaction involving material set is difficult to interpret, as words corresponding to physical or social threat were not frequency-matched with each other. The other interaction, concerned with valence (threat vs non-threat) is illustrated in Table 3. It can be seen that the anxious group took significantly longer to colour-name all cards [F( 1,46) = 12.5, P < O.OOl], but while control Ss took a similar length of time for both threat and non-threat words, anxious Ss were slower for threat than they were for non-threat words. Analysis of data for anxious and control Ss separately showed no significant differences between threat and non-threat words for control Ss, but highly significant differences for anxious Ss [F(l, 46) = 15.0, P < O.OOl].

Further analysis of colour-naming times in anxious Ss was carried out after dividing the whole group according to the threat domain reported as most worrying. Thirteen Ss indicated that they found health-related concerns to be most worrying, while 8 reported more concern with social worries. Three Ss could not choose between the two domains and were therefore excluded from this analysis. Analysis of variance was carried out using the 21 relevant Ss to examine for effects due to subgrouping, valence and materials as before.

There were significant main effects of valence, an interaction between valence and materials, and of greater importance, a three-way interaction between subgroup, valence and materials [F(l, 19) = 7.2, P cc 0.011. This last interaction reflected the fact that although colour-naming times were generally longer for threat than for non-threat words, in the case of Ss more concerned with social worries, colour-naming physical threat words actually took 4 set less than the time required for the frequency-matched control words (see Table 4). This is in marked contrast to those complaining of physical-health worries, who took 5 see longer to colour-name the physical threat words. In the case of the social threat cards. both subgroups required longer for the threat material than they did with the matched control card. It thus seems that all anxious Ss were disrupted in the colour-naming task by the presence of social threat words. whereas only those who are aware of physical worries are equally disrupted by physical threat words.

Threat cues in anxiety states

Table 4. Mean time (in set) for anxiety subgroups reporting different worries, to colour-name words related to each threat domain

Ss reporting Ss reporting physical worries socral worries

Material set (N = 13) (N = 8)

PhysIcal threat 86.8 13.5 Control card 81.8 77.8 DilTerence 5.0 -4.3 Social threat 82.9 76.8 Control card 78.9 71.6 Difkence 4.0 5.2

To investigate whether the longer colour-naming times for threat words were associated with greater awareness of word content, and hence better recognition memory, the data from the recognition test was subjected to a signal-detection analysis. Of those items that anxious SS claimed to recognize. 707; were correctly identified (73% threat and 66% non-threat), compared with 78% accuracy in the case of controls, for both threat and non-threat words. Values of sensitivity (d’) and response bias (p) were calculated for each type of material separately for each S (McNicol, 1972). The values of d' and p were then separately subjected to analyses of variance, carried out as before. The analysis of d’-values revealed only two main effects, for valence and type of material. Since no interaction with group was involved, it can be concluded that there were no differences

in the accuracy of recognition between the groups. In the case of b-values, the only significant effect was that for groups [F(1,46) = 4.89, P < 0.051. Since there was no interaction involving valence or type of material, it is clear that this response bias is a general effect, and is not dependent on word content. There were no indications that any S could accurately recall the colours of individual words. and no further analysis of this data was carried out.

Summarizing the results presented so far, there seems to be good evidence of selective interference with colour-naming of threat-related words, which is shown only by anxious Ss. Furthermore, there is some evidence, at least for physical threat words, that this effect is related to conscious cognitive content. On the other hand, there was no evidence that anxious Ss selectively encoded threat word content in the colour-naming task to the extent that this might be expected to facilitate recognition memory.

In a final type of analysis, an attempt was made to see which of the questionnaire measures was most closely associated with the disruption of colour-naming threat vs non-threat words. Pearson’s product-moment correlations were calculated between disruption scores (based on the difference in colour-naming time for threat vs non-threat material) and the other questionnaire measures obtained; Spielberger STAI and BDI. Correlations calculated for all Ss, and for each group separately, are shown in Table 5, where it can be seen that both Anxiety and Depression scores significantly predicted the extent of disruption. Within anxious Ss, only the correlation with State Anxiety approached significance, suggesting that this was the most important factor. However, any conclusions are made equivocal by the fact that all the Anxiety and Depression scores were interrelated. An attempt was made to disentangle the various measures and find out which was contributing most to the disruption effect, using partial correlations. State Anxiety was still significantly correlated with colour-naming disruption scores, after Trait Anxiety or Depression scores had been partialled out (0.4 and 0.32, respectively). On the other hand, the effect of partialling out State Anxiety scores from the other measures was to reduce correlations to non-significant levels (with BDI, 0.16; with Trait Anxiety. 0.004).

Table 5 Producr-moment correlations between quesrion- “are measures and degree of slowng mvolved m colour-

naming threat words

All Anxious Control Measure SS ss SS

Stare Anxiet) 0.53.’ 0.40’ 0.17 Trau Anxleg 0.37** 0.15 -0.02 BDI 0.47** 0.25 0.05

‘P < 0.1. **p < 0.01

568 ANDREW MATHEWS and Corm MACLEOD

Finally, since there was a significant difference between the groups in MHVT scores. the overall correlation between MHVT and colour-naming disruption was calculated. This revealed a marginally significant correlation (-0.29, P < 0.05) with lower MHVT scores being associated with more disruption. However, with State Anxiety scores partialled out the correlation was further reduced to -0.2 (NS), while partialling out MHVT scores from the correlation between State Anxiety and disruption scores left it highly significant (0.49, P < 0.001).

DISCUSSION

The main finding of this study was that although generally anxious Ss were slower in colour-naming all the words used, they were particularly slow in the case of words related to threat. Some difficulties of interpretation might be thought to arise from the overall slower performance of anxious Ss. The significant interaction between group and valence (threat vs non-threat) could

be due to the general tendency of anxious Ss to perform more poorly. relative to non-anxious Ss. as tasks become more difficult. Such performance inefficiencies are well-documented (e.g. Spiel- berger, 1966) and have been attributed to a loss in information-processing capacity, such as reduced space in working memory (e.g. Eysenck, 1977). If colour-naming threatening words is a relatively difficult task in some sense, then a selective performance deficit might be associated with anxiety states.

Such an explanation seems hard to maintain in the light of the difference in colour-naming times for material related to different threat domains: only those Ss who reported worrying about their health were further slowed by the physical threat words. Any explanation based on the general effects of anxiety or emotional arousal clearly encounters difficulties in accounting for this degree of specificity.

This striking specificity also suggests that explanations based exclusively on current mood state are incomplete. It is clear that mood state can account for the general slowing shown by our anxious Ss on all emotional material (cf. Bower, 1981), but not for the variations in this effect for different types of threat. Despite this, the results of the correlational analysis strongly implicate current anxiety state as a crucial factor, as opposed to trait anxiety or depression. Conceivably. the apparent specificity of the interference effect could be attributed to the effects of current mood. if physical threat words only show colour-naming disruption when anxiety is particularly high, and the Ss who reported physical worries happened to have higher State Anxiety scores. In fact, there were no significant differences between subgroups in any questionnaire measure, and if anything the Ss with social worries had higher scores (physical Ss, State = 46, Trait = 48; social Ss, State = 47, Trait = 56). It therefore seems that although state anxiety is clearly implicated in the interference effect, some other difference between subgroups must account for the different pattern of results according to type of threat material.

The most obvious candidate for this difference is that the content of worries reported by Ss in the different subgroups corresponds to differences in the danger schemata that are currently activated. It would appear that interference effects are particularly strong when the contents of a currently active danger schema match the type of threat cues presented. The fact that those with social worries were actually faster at colour-naming physical threat words than the related control words, is powerful evidence that state anxiety per se is not sufficient to produce interference. Rather. it is necessary both that the relevant danger schema should be currently active, and that state anxiety should be elevated. This is clearly demonstrated by the finding that interference with colour-naming physical threat words was shown exclusively by anxious individuals. but only if they also reported health worries.

The hypothesis that an exact match between a currently active danger schema and the threat cues presented is a necessary condition for interference, might seem to be challenged by the finding that both subgroups of anxious patients were slowed by social threat words. However, we did not select subgroups as worrying exclusively about one topic, but rather by having Ss select their main source of worry. Thus it may well be that all anxious individuals have social worries. but some of them also have worries about their physical health. If such physical concerns are emphasized by the S, despite the presence of both types of worry, then the pattern of results obtained becomes more understandable. Perhaps social concerns are primary, and physical health worries develop

Threat cues in anxiety states 569

secondarily in some Ss due to misinterpretation of physiological reactions in a catastrophic way. Alternatively. health worries may be primary in some Ss, but social concerns also develop due to the possibility of dispIaying panic of loss of control in pubhc.

Regardless of the exact interpretation of the results found within anxiety subgroups, important questions remain about the mechanisms involved in the more general interference effect shown by all anxious Ss. If we assume that the effect does indeed depend on the availability and activation of specific knowledge structures, in this case concerning personal threat, then our findings are consistent with the usually accepted interference explanation of the Stroop phenomenon. It may be that anxiety Ss maintain such danger schemata in relatively permanent states of activation. Alternatively, these structures may be more easily activated in anxious individuals whenever relevant input is encountered.

An alternative but related explanation is that Ss normally minimize Stroop interference by maintaining a voluntary attentional set, aimed at reducing the degree of processing accorded to the irrelevant stimulus. in this case word content (see Harvey, 1984). According to this explanation, interference increases over trials because of the difficulty in maintaining this attentional set. Emotional arousal may lead to difficulty in maintaining such an attentional set and as a result produces greater Stroop interference. Specific effects due to the individual meaning of words could therefore arise because their perception produces greater emotional arousal in Ss with related worries.

There thus seem to be two related explanations for the specificity of the effects we have reported: one assumes that biased processing of threat cues gives rise to interference directly, while the other assumes that it is the emotional arousal arising from perception of relevant words that slows colour-naming, perhaps by disrupting attentional set. Clearly the explanations are not incompat- ible. and both may operate simultaneously. However, it would seem that the latter predicts elimination of the effect with successful treatment, while the former does not necessarily make such a prediction. Work is currently in progress to test out the consequences of treatment that may throw light on this issue. Whatever the outcome, the Stroop phenomenon offers considerable promise as an objective indicator of current concern, and a means of investigating cognitive theories of mood disorder.

Acknou,l~rip~mmrs-Helpful comments on an earlier version of this paper were provided by Frazer Watts, Mark Williams, Michael Eysenck and David Clark.

This research was supported by a grant from the Medical Research Council, U.K.

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